1. Field of the Invention
The present invention relates to a drafting mechanism and, more specifically, to an improvement of a unit drafting mechanism to be incorporated into a spinning machine such as a drawing frame, a comber, or a lap former, for doubling and roller-drafting slivers.
2. Description of the Related Art
As is generally known, in a conventional drafting mechanism for a spinning frame, such as a drawing frame, a pair of slide metals are disposed on the roller stands facing each other. A plurality, for example, three or four, of bottom rollers and top rollers are journaled on these slide metals and clearer pads are disposed at positions below corresponding bottom rollers in contact thereto and swing in a direction along the delivering direction of slivers supplied to the drawing frame. An Ermen's clearer provided with an endless clearing belt is rotatably disposed above the top rollers in contact thereto so that flies adhered to the top rollers and the bottom rollers can be removed therefrom. As disclosed in Japanese Examined Utility Model Publication (KOKOKU)No. 56-23337 and Japanese Unexamined Utility Model Publication (KOKAI)No. 57-188884, a conventional bottom roller has a fluted working section, journals supported in bearings on the slide metals, and cylindrical neck sections formed between the fluted working section and the corresponding one of the journals. A conventional top roller has a smooth working section provided with a smooth cylindrical surface extending between the slide metals and facing the fluted working section of the corresponding bottom roller.
The working section of the bottom roller of the conventional drafting mechanism is provided with many flutes extending along the axial direction thereof and formed in the circumferential portion thereof in a substantially parallel condition. When the drafting mechanism is driven at high speed, an accompanying air stream is created at a portion around the facing top roller and bottom roller by high speed rotation of the rollers. Most of the accompanying air stream tends to flow in the axial direction along the contact line between the top rollers and bottom roller and along the line of contact of the working sections of the top and bottom rollers and the clearer members. Accordingly, when such an accompanying air stream passes the end portions of the roller, it disperses around the neck portions of the top roller and the bottom roller together with flies. Such flies adhere to the neck portions of these rollers and finally are introduced into a fiber fleece being processed by the drafting mechanism. This phenomenon has been recognized as a serious problem impairing the quality of slivers delivered from such a drafting mechanism.
The applicants of the present application proposed previously a drafting mechanism capable of intercepting such accompanying axial air flows to prevent the disturbance of the smooth arrangement of fibers in the processing fleece, as disclosed in Japanese Unexamined Patent Publication (KOKAI)No. 62-191522. This drafting mechanism employs top and bottom rollers having working sections of lengths substantially equal to the distance between the slide metals and intercepts the accompanying axial air flows by the inside surfaces of the slide metals.
However, this known, improved drafting mechanism still has drawbacks in that the accompanying axial air flows flowing toward the opposite ends of the working sections carry flies into gaps between the journals of the bottom roller and the corresponding bearings to cause seizure. Further, flies aggregate around the slide metals and around the circumference of the top and bottom rollers and drop into the processing fleece to impair the quality of the slivers in process. Furthermore, when rotated at a high speed, the bottom roller is heated by friction and damages the rubber coating of the top roller or adversely affects the quality of the fleece.